It is known to incorporate a security feature into a valuable item, such as a banknote, to provide a recipient of the item with evidence of the item's authenticity. If a single security feature is used on all items of the same type (for example, all twenty dollar bills), then once the single security feature is compromised, that type of item can be compromised at will by counterfeiters.
It would be desirable to be able to reduce the possibility of an item being compromised even if the security feature protecting that item is compromised.